NASA Ames: P. Russell, J. Redemann, S. Dunagan, NASA Ames: P. Russell, J. Redemann, S. Dunagan, R. Johnson, J. ZavaletaR. Johnson, J. Zavaleta

PNNL: B. Schmid, C. Flynn, E. KassianovPNNL: B. Schmid, C. Flynn, E. Kassianov

NASA GSFC: AERONET TeamNASA GSFC: AERONET Team

A collaboration involving:A collaboration involving:

4S4STARTAR::

SSpectrometer for pectrometer for SSky-ky-SScanning, canning, SSun-un-TTracking racking AAtmospheric tmospheric RResearchesearch

4STAR:4STAR: Spectrometer Spectrometer for for Sky-ScanningSky-Scanning, , Sun-TrackingSun-Tracking

Atmospheric ResearchAtmospheric Research

AATS-14 - like column and profiles • Aerosol• H2O• O3

AERONET-like

• Phase function• Size mode distributions• nre(), nim()• Single-scattering albedo • Asymmetry parameter • Shape• Hence aerosol type

Improve H2O, O3

Add NO2 Thus improve AOD

Simultaneous spectra yield airborne profiles of aerosol type via Aeronet-like retrievals

300 400 500 600 700 800 900 10000

1

2

3

4

5

6

x 104

Wavelength (nm)

Co

un

ts

4STAR and its Use4STAR and its Use

AATS-14

AATS-6

NASA Ames NASA Ames Airborne Tracking Airborne Tracking SunphotometersSunphotometers

Since 1996Since 1996• 13 Field Campaigns13 Field Campaigns• >70 Publications>70 Publications

Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research

(4STAR)(4STAR)

Fiber Optics Rotating Joint

Azimuth Motor

Elevation Motor

Motor Feedback Devices

Aircraft Skin

Fiber Optics CableOptical Entrance Sun Tracking Head

Slip Ring

Optical Entrance

Key Technological HurdlesKey Technological Hurdles

1.1. Maintaining calibration to 1% over a period Maintaining calibration to 1% over a period of monthsof months

2.2. Stray light rejection: measure skylight Stray light rejection: measure skylight within 3° of sunwithin 3° of sun

3.3. Fiber optic couplings with <1% calibration Fiber optic couplings with <1% calibration stability (Connections/Rotation)stability (Connections/Rotation)

4.4. Sky scan within 100 seconds(10 km in Sky scan within 100 seconds(10 km in flight)flight)

`̀

Quasi-monolithic, no moving parts, ceramic body, Range: 250-1016 nm, Resolution ~ 2 nm

Zeiss MCS CCD spectrometer

Ground Prototype (4STAR-Ground)Ground Prototype (4STAR-Ground)

4STAR-Ground

AATS-14

Direct Beam ComparisonDirect Beam Comparison

Direct Beam ComparisonDirect Beam ComparisonAATS-14 & 4STAR-GroundAATS-14 & 4STAR-Ground

Transmittance

UT

4STAR-Ground4STAR-Ground

AERONET CimelAERONET Cimel

Jens RedemannJens Redemann

Roy JohnsonRoy Johnson

Radiance CalibrationRadiance Calibration

4STAR-Ground4STAR-GroundAERONET CimelAERONET Cimel

NASA Ames 30” SphereNASA Ames 30” Sphere

-40 -20 0 20 40 60 80 100 120

100

101

102

scattering angle (deg)

uW/(

cm2 .s

r.nm

)

4STAR and Aeronet principal plane scans on 2007-04-30, SZA=43.8 degIndependently calibrated at NASA Ames and NASA GSFC

+ 4STARo Aeronet

440.8 nm

673.6 nm869.3 nm

1005.6 nm

4STAR and AERONET principal plane scan4STAR and AERONET principal plane scan

Straylight rejection close to SunStraylight rejection close to Sun

Size Distribution Retrieval Size Distribution Retrieval using AERONET Codeusing AERONET Code

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.1 1 10

NASA_AMES

4STAR, 04/27/2007,21:50AERONET, 04/27/2007,21:37

dV

/dln

R

Particle Radius, m

Rotating Fiber Optics CouplingRotating Fiber Optics CouplingThroughput Repeatability Throughput Repeatability

Next steps…Next steps…• New collector design, 100X light volume. New collector design, 100X light volume.

Goal: Sky-scan measurements within 100 Goal: Sky-scan measurements within 100 seconds, 10 km in flightseconds, 10 km in flight

• Mauna Loa, spectral Langley calibrationMauna Loa, spectral Langley calibration• Add SWIR spectrometer for more size and Add SWIR spectrometer for more size and

absorption informationabsorption information• Continue spectral inversion developmentContinue spectral inversion development• Harden design for airborne deploymentHarden design for airborne deployment• Deploy in 2011: Western Atlantic Deploy in 2011: Western Atlantic

Tropospheric Aerosol Campaign (WATAC)Tropospheric Aerosol Campaign (WATAC)